1. Field of the Invention
This invention relates to a panel ceiling having a grid framework that supports the panels. The grid is directly attached to an overhead structure such as an existing ceiling.
2. Background Art
The most common form of panel ceiling wherein a grid framework supports acoustical panels, is a suspended ceiling. Main beams of the grid are suspended on hanger wires anchored in an overhead structure. The grid, or a section thereof, of parallel main beams and interlocking, intersecting cross beams, is assembled, and hung, from the overhead structure, before the panels are inserted. In assembling the grid, the main beams can be separated and rotated as required to insert cross beam end connectors.
In such a ceiling, the hanger wires, in suspending the grid, create space between the overhead structure and the grid. This space is generally used, particularly in commercial construction, for utilities, such as air ducts and electrical conduits.
The space is also useful in connecting the cross beams to the main beams, and in placing panels into the assembled grid.
The main beams are hung by wires, and then the cross beams and main beams are maneuvered, using the space, to interlock the beams to assemble the grid. The main beams can be separated and rotated during the assembly.
In the assembled grid, the panels are inserted through the grid openings into the space above the grid, and then maneuvered into place on the grid. Sufficient space above the grid is required to so place the panels in a suspended ceiling.
A substantial body of prior art exists with respect to such suspended ceilings, since they possess many advantages and are extensively used.
A disadvantage of a suspended ceiling is that it consumes overhead space which is sometimes more needed below the ceiling than above the ceiling.
In another form of panel ceiling having a grid, the grid, through the main beams, is directly attached Go an overhead structure, eliminating the space between the overhead structure and the grid, and any use of hanger wires. Such a direct attachment is particularly desirable in residential structures where an old ceiling is being covered, in order to minimize loss of ceiling height.
In eliminating the space between the overhead structure and grid, however, other problems are created.
Whereas in the wire suspended grid, the main beams can be shifted during the installation of the cross beams, in direct attached grid, the main beams are first fixed in place, and then the cross beams are installed. The main beams cannot be shifted during a connection. Hence, the numerous different connections between the main beams and cross beams developed for suspended ceilings are not suitable for direct attached grid ceilings.
Another problem with direct attached grid ceilings, is the lack of space above the direct attached grid for placing panels. Again, this renders the extensive prior art relating to suspended ceilings inadequate to solve the problems of assembling grid, and placing panels, encountered in direct applied grid ceilings.
These problems encountered with direct applied grid have discouraged any wide spread use.
Attempts have been made to solve these problems. U. S. Pat. No. 4,920,719, incorporated herein by reference, creates space for placing panels and cross beams on the fixed main beams by the use of a stepped cross-section in the main beam which is directly attached to the ceiling. A panel is shifted into position using the space created by an upper stepped portion of such main beam, and a cross beam is then placed to help support the panel.
In the ""719 patent however, a cross beam, which must be placed after a panel is in place, does not positively lock into the main beams at a predetermined location, but rather the cross beam can slide along the main beam. An installer must use judgment in locating the panels and cross beams, to keep the panels and cross beams desirably aligned to present a uniform ceiling appearance. Such a procedure is time consuming and often the end result is unsatisfactory in that the panels are misaligned, and free to shift.
The prior art connections between the main and cross beams developed for suspended ceilings do not work with direct attached grid. As described above, prior art grid connections in suspended ceilings require space to assemble the connections, and require main beam movement during assembly. Both these requirements are lacking in direct attached grid.
In a directly attached grid, directly attached main beams are slotted in such a way that connectors on the ends of the cross beams can be locked to the main beam at factory predetermined positions on the main beam. This aligns and secures the cross beams and panels in the ceiling in an orderly and uniform manner. A stepped slot enables the cross beams to be so locked.
The stepped slot has portions that necessarily extend in the web and in the adjacent step of the stepped main beam, and optionally in the riser adjacent to that step.
In assembling the grid on site, a cross beam is locked to a stepped main beam that is directly attached to an overhead structure. The cross beam is locked to the main beam, both along the main beam, as well as laterally of the main beam, at factory predetermined positions along the main beam. There is no judgment required of the installer in positioning the cross beams and panels after the main beams are aligned, spaced, and secured to the overhead structure. The end result is a uniform, secure, easily installed ceiling, with an interlocking grid. The panels are not free to shift. The ceiling face can be installed within one and one-half inches of an existing overhead structure.
The ceiling can be disassembled, beginning at any point, and to any extent. Panels can be shifted above other panels for access to any point above the ceiling. The stepped slot of the invention further permits individual cross beams to be readily removed by vertical motion from a completed ceiling, and a given panel removed, without disturbing other panels in the ceiling.
The stepped slot of the invention exists in the main beam in a way that does no significantly reduce the strength of the main beam. The strength of the beam remains adequate to support the panels and cross beams.
The slot permits a cross beam to use the clearance created by the stepped beam to position and lock the cross beam to the main beam.
The stepped slot likewise permits the necessary clearance to unlock a cross beam from the main beam to permit an adjacent panel to be removed from a completed ceiling.
The horizontal portion of the stepped slot is critical to the invention, since it permits the connector on the cross beam to be shifted downward from its position above the step to hook onto the web. Main beam separation or twist is not necessary to achieve this connection.
The grid system of the invention can optionally be produced of metal, or of plastic. Where the grid is produced of plastic, the main and cross beam may be extruded to produce, for each, a uniform profile. The slots and the connectors are then formed by a cutting, in a stamping operation. The connectors are then offset, again in the stamping operation. Since the main beams are attached directly to an upper structure, the necessary rigidity of the grid is obtained from such upper structure. The stepped slot of the invention, wherein material is removed from the main beam, does not significantly detract from the strength obtained in the grid system by attaching the main beams directly to the overhead structure.